[patch 65/96] USB: EHCI: slow down ITD reuse

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Karsten Wiese <fzu@xxxxxxxxxxxxxxxxxxxxx>

commit 9aa09d2f8f4bc440d6db1c3414d4009642875240 upstream.

Currently ITDs are immediately recycled whenever their URB completes.
However, EHCI hardware can sometimes remember some ITD state.  This
means that when the ITD is reused before end-of-frame it may sometimes
cause the hardware to reference bogus state.

This patch defers reusing such ITDs by moving them into a new ehci member
cached_itd_list. ITDs resting in cached_itd_list are moved back into their
stream's free_list once scan_periodic() detects that the active frame has
elapsed.

This makes the snd_usb_us122l driver (in kernel since .28) work right
when it's hooked up through EHCI.

[ dbrownell@xxxxxxxxxxxxxxxxxxxxx: comment fixups ]

Signed-off-by: Karsten Wiese <fzu@xxxxxxxxxxxxxxxxxxxxx>
Tested-by: Philippe Carriere <philippe-f.carriere@xxxxxxxxxx>
Tested-by: Federico Briata <federicobriata@xxxxxxxxx>
Signed-off-by: David Brownell <dbrownell@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/usb/host/ehci-hcd.c   |    2 +
 drivers/usb/host/ehci-mem.c   |    1 
 drivers/usb/host/ehci-sched.c |   56 ++++++++++++++++++++++++++++++++++++------
 drivers/usb/host/ehci.h       |    6 ++++
 4 files changed, 57 insertions(+), 8 deletions(-)

--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -87,6 +87,10 @@ struct ehci_hcd {			/* one per controlle
 	int			next_uframe;	/* scan periodic, start here */
 	unsigned		periodic_sched;	/* periodic activity count */
 
+	/* list of itds completed while clock_frame was still active */
+	struct list_head	cached_itd_list;
+	unsigned		clock_frame;
+
 	/* per root hub port */
 	unsigned long		reset_done [EHCI_MAX_ROOT_PORTS];
 
@@ -208,6 +212,8 @@ timer_action (struct ehci_hcd *ehci, enu
 	}
 }
 
+static void free_cached_itd_list(struct ehci_hcd *ehci);
+
 /*-------------------------------------------------------------------------*/
 
 /* EHCI register interface, corresponds to EHCI Revision 0.95 specification */
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -485,6 +485,7 @@ static int ehci_init(struct usb_hcd *hcd
 	 * periodic_size can shrink by USBCMD update if hcc_params allows.
 	 */
 	ehci->periodic_size = DEFAULT_I_TDPS;
+	INIT_LIST_HEAD(&ehci->cached_itd_list);
 	if ((retval = ehci_mem_init(ehci, GFP_KERNEL)) < 0)
 		return retval;
 
@@ -497,6 +498,7 @@ static int ehci_init(struct usb_hcd *hcd
 
 	ehci->reclaim = NULL;
 	ehci->next_uframe = -1;
+	ehci->clock_frame = -1;
 
 	/*
 	 * dedicate a qh for the async ring head, since we couldn't unlink
--- a/drivers/usb/host/ehci-mem.c
+++ b/drivers/usb/host/ehci-mem.c
@@ -128,6 +128,7 @@ static inline void qh_put (struct ehci_q
 
 static void ehci_mem_cleanup (struct ehci_hcd *ehci)
 {
+	free_cached_itd_list(ehci);
 	if (ehci->async)
 		qh_put (ehci->async);
 	ehci->async = NULL;
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -1004,7 +1004,8 @@ iso_stream_put(struct ehci_hcd *ehci, st
 
 		is_in = (stream->bEndpointAddress & USB_DIR_IN) ? 0x10 : 0;
 		stream->bEndpointAddress &= 0x0f;
-		stream->ep->hcpriv = NULL;
+		if (stream->ep)
+			stream->ep->hcpriv = NULL;
 
 		if (stream->rescheduled) {
 			ehci_info (ehci, "ep%d%s-iso rescheduled "
@@ -1653,14 +1654,28 @@ itd_complete (
 			(stream->bEndpointAddress & USB_DIR_IN) ? "in" : "out");
 	}
 	iso_stream_put (ehci, stream);
-	/* OK to recycle this ITD now that its completion callback ran. */
+
 done:
 	usb_put_urb(urb);
 	itd->urb = NULL;
-	itd->stream = NULL;
-	list_move(&itd->itd_list, &stream->free_list);
-	iso_stream_put(ehci, stream);
-
+	if (ehci->clock_frame != itd->frame || itd->index[7] != -1) {
+		/* OK to recycle this ITD now. */
+		itd->stream = NULL;
+		list_move(&itd->itd_list, &stream->free_list);
+		iso_stream_put(ehci, stream);
+	} else {
+		/* HW might remember this ITD, so we can't recycle it yet.
+		 * Move it to a safe place until a new frame starts.
+		 */
+		list_move(&itd->itd_list, &ehci->cached_itd_list);
+		if (stream->refcount == 2) {
+			/* If iso_stream_put() were called here, stream
+			 * would be freed.  Instead, just prevent reuse.
+			 */
+			stream->ep->hcpriv = NULL;
+			stream->ep = NULL;
+		}
+	}
 	return retval;
 }
 
@@ -2101,6 +2116,20 @@ done:
 
 /*-------------------------------------------------------------------------*/
 
+static void free_cached_itd_list(struct ehci_hcd *ehci)
+{
+	struct ehci_itd *itd, *n;
+
+	list_for_each_entry_safe(itd, n, &ehci->cached_itd_list, itd_list) {
+		struct ehci_iso_stream	*stream = itd->stream;
+		itd->stream = NULL;
+		list_move(&itd->itd_list, &stream->free_list);
+		iso_stream_put(ehci, stream);
+	}
+}
+
+/*-------------------------------------------------------------------------*/
+
 static void
 scan_periodic (struct ehci_hcd *ehci)
 {
@@ -2115,10 +2144,17 @@ scan_periodic (struct ehci_hcd *ehci)
 	 * Touches as few pages as possible:  cache-friendly.
 	 */
 	now_uframe = ehci->next_uframe;
-	if (HC_IS_RUNNING (ehci_to_hcd(ehci)->state))
+	if (HC_IS_RUNNING(ehci_to_hcd(ehci)->state)) {
 		clock = ehci_readl(ehci, &ehci->regs->frame_index);
-	else
+		clock_frame = (clock >> 3) % ehci->periodic_size;
+	} else  {
 		clock = now_uframe + mod - 1;
+		clock_frame = -1;
+	}
+	if (ehci->clock_frame != clock_frame) {
+		free_cached_itd_list(ehci);
+		ehci->clock_frame = clock_frame;
+	}
 	clock %= mod;
 	clock_frame = clock >> 3;
 
@@ -2277,6 +2313,10 @@ restart:
 			/* rescan the rest of this frame, then ... */
 			clock = now;
 			clock_frame = clock >> 3;
+			if (ehci->clock_frame != clock_frame) {
+				free_cached_itd_list(ehci);
+				ehci->clock_frame = clock_frame;
+			}
 		} else {
 			now_uframe++;
 			now_uframe %= mod;


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